Go in store if you fail with the second esim, it was painful getting to activated on Wednesday but the procedure should be a little more known by now (it took over an hour and a half to activate one on Wednesday).
The eSim isn’t without issues though, sending texts from the secondary sim is a bit problematic and unless you use 12.1.1 you can’t switch the sim off without using Airplane mode and effectively switching both off.
There is a UK eSim thread with plenty of discussion in it.
https://forums.macrumors.com/threads/uk-esim-dual-sim-thread.2150657/